1. Field of the Invention
The present invention relates to a manual air pump for inflating, e.g., bicycle tires, and more particularly to a dual-mode manual air pump that provides at least two selectable modes for inflation.
2. Description of the Related Art
Bicycle pumps include two typical types: 1) big bore for high volume per stroke and low pressure for rapid inflation, yet high pressure operation is difficult to achieve; and 2) small bore for low volume per stroke and high pressure for inflating bicycle tires to high pressure. Various designs in manual air pumps having selectable high volume and high pressure modes have been proposed, wherein the pump in one mode provides a very high volume of air per pump stroke and in another mode provides less volume per stroke but enables the user to inflate to higher pressures. An example of such manual air pumps is disclosed in U.S. Pat. No. 5,443,370 issued to Wang on Aug. 22, 1995. Yet, there are only two inflation modes provided. The present invention is intended to provide a manual air pump that provides at least two selectable modes for inflation.
It is an object of the present invention to provide a manual air pump that provides selectable high pressure and high volume modes for inflation.
It is another object of the present invention to provide a manual air pump that provides three selectable inflation modes.
In accordance with a first aspect of the invention, a manual air pump comprises:
an outer cylinder comprising a first chamber and including a first end and a second end,
a head provided to the second end of the outer cylinder, the head including an outlet passage communicated with the first chamber for supplying air to an object to be inflated,
an inner cylinder securely mounted in the first chamber of the outer cylinder and including a first end secured in the second end of the outer cylinder and a second end, the inner cylinder defining a second chamber that is communicated with the outlet passage,
a piston rod having a first end with a piston slidably received in the first chamber of the outer cylinder and a second end extended beyond the outer cylinder, the piston separating the first chamber into a first chamber section adjacent to the head and a second chamber section distal to the head, the piston rod defining a third chamber therein,
a handle secured to the second end of the piston rod to move therewith,
a plug securely mounted to the second end of the inner cylinder and in sliding contact with an inner periphery defining the third chamber of the piston rod, the plug separating the second chamber into a third chamber section distal to the handle and a fourth chamber section adjacent to the handle, the plug having a one-way valve mounted therein such that air is only flowable from the fourth chamber section into the third chamber,
means for supplying ambient air into the second chamber section and the fourth chamber section during an outward stroke of the handle away from the head, and
a release valve means for optionally communicating the fourth chamber section with outside,
whereby reciprocating movement of the handle causes high volume/low pressure inflation when the release valve means is in an inoperative status such that the fourth chamber section is not communicated with outside, and reciprocating movement of the handle causes low volume/high pressure inflation when the release valve means is in an operative status such that the fourth chamber section is communicated with outside.
In accordance with a second aspect of the invention, a manual air pump comprises:
an outer cylinder comprising a first chamber and including a first end and a second end,
a head provided to the second end of the outer cylinder, the head including an outlet passage communicated with the first chamber for supplying air to an object to be inflated,
an inner cylinder securely mounted in the first chamber of the outer cylinder and including a first end secured in the second end of the outer cylinder and a second end, the inner cylinder defining a second chamber that is communicated with the outlet passage,
a piston rod having a first end with a piston slidably received in the first chamber of the outer cylinder and a second end extended beyond the outer cylinder, the piston separating the first chamber into a first chamber section adjacent to the head and a second chamber section distal to the head, the piston rod defining a third chamber therein,
a handle secured to the second end of the piston rod to move therewith,
a plug securely mounted to the second end of the inner cylinder and in sliding contact with an inner periphery defining the third chamber of the piston rod, the plug separating the second chamber into a third chamber section distal to the handle and a fourth chamber section adjacent to the handle, the plug having a one-way valve mounted therein such that air is only flowable from the fourth chamber section into the third chamber,
means for supplying ambient air into the second chamber section and the fourth chamber section during an outward stroke of the handle away from the head, and
a release valve means for optionally communicating the first chamber section with outside,
whereby reciprocating movement of the handle causes high volume/low pressure inflation when the release valve means is in an inoperative status such that the first chamber section is not communicated with outside, and reciprocating movement of the handle causes low volume/high pressure inflation when the release valve means is in an operative status such that the first chamber section is communicated with outside.
In accordance with a third aspect of the invention, a manual air pump comprises:
an outer cylinder comprising a first chamber and including a first end and a second end,
a head provided to the second end of the outer cylinder, the head including an outlet passage communicated with the first chamber for supplying air to an object to be inflated,
an inner cylinder securely mounted in the first chamber of the outer cylinder and including a first end secured in the second end of the outer cylinder and a second end, the inner cylinder defining a second chamber that is communicated with the outlet passage,
a piston rod having a first end with a piston slidably received in the first chamber of the outer cylinder and a second end extended beyond the outer cylinder, the piston separating the first chamber into a first chamber section adjacent to the head and a second chamber section distal to the head, the piston rod defining a third chamber therein,
a handle secured to the second end of the piston rod to move therewith,
a plug securely mounted to the second end of the inner cylinder and in sliding contact with an inner periphery defining the third chamber of the piston rod, the plug separating the second chamber into a third chamber section distal to the handle and a fourth chamber section adjacent to the handle, the plug having a one-way valve mounted therein such that air is only flowable from the fourth chamber section into the third chamber,
means for supplying ambient air into the second chamber section and the fourth chamber section during an outward stroke of the handle away from the head,
a first release valve means for optionally communicating the fourth chamber section with outside,
a second release valve means for optionally communicating the first chamber section with outside,
whereby reciprocating movement of the handle causes high volume/low pressure inflation when the first release valve means is in an inoperative status such that the fourth chamber section is not communicated with outside and the second release valve means is in an inoperative status such that the first chamber is not communicated with outside,
whereby reciprocating movement of the handle causes medium volume/medium pressure inflation when the first release valve means is in an operative status such that the fourth chamber section is communicated with outside and the second release valve means is in an inoperative status such that the first chamber section is not communicated with outside, and
whereby reciprocating movement of the handle causes low volume/high pressure inflation when the first release valve means is in an inoperative status such that the fourth chamber section is not communicated with outside and the second release valve means is in an operative status such that the first chamber section is communicated with outside.